Automatic gas alarm



May 22, 19% X 234mm AUTOMATIC GAS ALARM Filed March 12, 1954 INVENTORERNEST cox gal 3 AUTQMATEC GAS ALARM Ernest Cox, Hempstead, N. Y.

Application March 12, 1954, Serial No. 415,788

1 Claim. (Cl. 340-237) The invention is a device intended forinstallation in dwellings and other buildings where natural gas,manufactured gas or both (hereinafter called gas) are used as fuel. Itsfunction is to sound an alarm and shut oil? the flow of gas at itssource in the building in the event of an undetected leak. Its purposeis to minimize the loss of life by asphyxiation and violent explosionwhich is incidental to the use of the gas as fuel.

The invention employs the difference in weights of equal volumes of gasand air which, using one cubic foot of each, would amount to .70 ounceapproximately at sea level. Any sealed volume balanced in atmosphereagainst an equal weight of less volume is partially supported by buoyantforce equal to the weight of air it displaces. It will descend ifsurrounded by a gas mixture of less weight and ascend when surrounded bya heavier mixture. To obtain a reaction to a comparatively harmless gasmixture, the invention must be of delicate construction, the movingparts must have a minimum of weight and friction and the electriccontacts must be sealed against possible ignition of gas.

One form of the invention is illustrated in the accompanying drawing inwhich Figure 1 is the entire assembly and wiring in perspective. Thedevice is placed above the window line of the building and convenient tothe gas outlet. An electric Wire lead 1 connects to terminal screw 22(see Figure 2) from source of current. Wire lead 2 connects from metalbushing 19 (see Figure 2) to solenoid shutoff 3 which is placed in gasline at source in building. Wire lead 4 connects from solenoid shutofi"3 to source of current. Wire lead 5 connects from lead 2. to alarm bell6 which is placed preferably on outside of building. Wire lead 7connects from alarm bell 6 to wire lead 4. It is the function of thedevice to bridge Wire leads 1 and 2 thus closing an electric circuitwhich will then actuate the solenoid shutoflf 3 thereby shutting off theflow of gas, and the alarm bell 6 which will indicate trouble. I amaware that the method of signal and shutoff set forth here is only oneof several possible arrangements, and since the wiring of this device isnot the essence of the invention, I submit this one for its clarity.

Figure 2, a vertical section through the assembly shows a sealed hollowfloat 8 through which is fixed vertically a rigid stem 9 hooked at theupper end and suspended from lever 10 which is hooked at the outer endand attached at the inner end to the outer coil of a flat spiral spring11.

Figure 3 is a right hand projection showing fiat spiral spring 11attached on the inside coil to a slot in adjustable shaft 12 which isthreaded through upright 13 and lock nut 14. It will be seen here thatby turn- 2,747,176 Patented May 22, 1956 ing shaft 12 so as to tightenspiral spring 11, the stem 9 and float 8 will rise and remain freelysuspended above the lower mechanism, and can be locked in any requiredposition.

in Figure 2 the base 15 constitutes a sealed switch box made ofnon-conducting material and with a deep bore in the center. A diaphragm16 suitably thin and fiexible, is sealed by gaskets 1717 on top andbottom and pressed between base 15 and cap 18 which has a hole throughcenter to freely accommodate bottom end of stem 9.

Through the center of base 15 is fixed a metal bushing 19 and attachedto this is electric wire lead 2. Through the center of bushing 19 isthreaded an adjustable contact screw 20. From a point directly abovecontact screw 20 and touching diaphragm 16 a thin brass contact spring21 slopes downward to base 15 and fastened by a terminal screw 22. Tothis is fastened electric wire lead 1. Four legs 23 are attached to base15.

In operation, float 8 and stem 9 are suspended by adjustment of spring11 so that bottom end of stem is within a very short striking distanceof diaphragm 16. In this position the float 8 is balanced in atmospherepartially by tension on spring 11 and partially by the buoyant force ofair equalling approximately the weight of air displaced by float 8.Adjustable contact screw 20 is adjusted to within a few thousandths ofan inch from the contact spring 21. (Since it is enclosed, this microadjustment is made by using a test light attached to terminal screw 22and bushing 19.)

When float 8 is surrounded by a gas mixture of lighter weight than air,the atmospheric buoyant force, which partially supports it, will havebeen reduced by the difference in weight of the original volume of airand the same volume of gas mixture and it will descend carrying the stem9 to strike diaphragm 16 and causing contact spring 21 to touch contactscrew 20. This contact bridges electric leads 1 and 2 and closes acircuit which actuates solenoid shutoff valve 3 and rings alarm bell 6.

I am aware of existing patents covering devices which employ a floatsuspended from a beam and balanced by a counterweight. My inventiondiffers in the method of suspension, which, as has been shown, is alever with a spring as the fulcrum. This eliminates most of the loss ofefficiency due to friction and reduces the cost of manufacture. Myinvention differs also in that it was designed to detect only gaseslighter than air.

I claim:

A device for signalling the presence of gas, and in particular,manufactured or natural gas, such as is used for fuel, comprising asealed hollow float and stem held in delicate suspension vertically inatmosphere by a lever and the tension on an adjustable flate spiralspring in such manner that when the float is surrounded by a gas ormixture of less weight than air, it will descend and strike thediaphragm of a sealed electric switch thus sounding an alarm andshutting the gas off at its source.

References Cited in the file of this patent UNITED STATES PATENTS826,659 Hanger July 24, 1906 943,015 Groesbeck Dec. 14, 1909 1,995,870Stone Mar. 26, 1935 2,675,816 Giannete Apr. 20, 1954

